NEW TYPE OF CONCRETE BRIDGE

Western Star, 19 August 1924, Page 2

NEW TYPE OF CONCRETE BRIDGE

Steadilv developing his powers as. a bridge builder, the reinforced concrete constructor undertakes to carry out designs hitherto regarded as outside ins province. If there is any type ot structure the steel bridge builder might have considered his. sole monopoly, it is the bowstring bridge, says the British Engineers: Export Journal., jn reference to a bridge of this type erected at Nantes. France. The essential feature is the support of the wad by Mastic arch-ribs. In such a structure the ability of the materials of which itis composed to withstand tensile stresses is, supremely important, and many architects and engineers have the opinion that reinforced concrete is weakest in regard to tensile stress. In tins French bridge, dependence has been placed on the tensile strength of the material. It has a span of about 180tt, has an overtoil width of 65ft 7m, with n roadway of , 32ft. 9in. carrying » double tramway track. From the centre of the main tie beams to the centre of the ribs there is a rise of 31it, giv:ii<.' the ratio of rise height to width of span commonly adopted as standard :in bowstring bridge construction. H"' vertical suspenders are perforated to lighten their weight without diminishing them in actual strength and to redn'eo further the dead weight of the ,lHM.cture, th'e cantilevered portions of the cross beams supporting the deck ■slab carrying the roadway are similarly treated. " A total of 212 tons of steel reinforcement was used in the br.dge.